Dual 2.5Ghz G5 LCS PIA issues again

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
Well here we go again! I turned both G5's off for a week and now they turn on but with no boot chime. Took out all the ram out and turned on then added one stick then all ram still nothing. On the one that was the better of the two i thought i had replaced the "o" rings but noticed the usual signs of leaking rings and replaced them, still nothing. also tried a different graphics card in each, no boot chime. I don't want to but may pull the logic boards to check the U3 heatsinks. These PM's are a real pain(had to break out my trusty G4 QS once again). Any other thoughts are appreciated
ty
 

Altemose

macrumors G3
Mar 26, 2013
9,173
480
Elkton, Maryland
Well here we go again! I turned both G5's off for a week and now they turn on but with no boot chime. Took out all the ram out and turned on then added one stick then all ram still nothing. On the one that was the better of the two i thought i had replaced the "o" rings but noticed the usual signs of leaking rings and replaced them, still nothing. also tried a different graphics card in each, no boot chime. I don't want to but may pull the logic boards to check the U3 heatsinks. These PM's are a real pain(had to break out my trusty G4 QS once again). Any other thoughts are appreciated
ty
PowerMac G5s require RAM to be installed in matched pairs. Check that the processors are properly seated and also check the heatsinks.
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
done and done. Did that, no red lights on which usually indicate an issue
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
yep like I said the better of the two G5's did have the crystals and I cleaned that then replaced the O rings. One machine apart so far
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
that will be my next step

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that was done on the other G5 still no boot chime but it powers on
 

Altemose

macrumors G3
Mar 26, 2013
9,173
480
Elkton, Maryland
that will be my next step

----------

that was done on the other G5 still no boot chime but it powers on
So you get no beeps even with the RAM and video card pulled? You should get beeps then add RAM and it may chime. If it does then re-add the video card.

Make sure that when you rebuilt the LCS that the pump is full of coolant.
 

gavinstubbs09

macrumors 65816
Feb 17, 2013
1,386
249
NorCal boonies ~~~by Reno sorta
I'll provide my feedback as I own a G5 with the crappy LCS. When I first got it, the thing would run but overheat. Took it apart, rebuilt it with new o-rings, 3/8 fuel line (a bit small on the inside, maybe cuts down on the pressure or something), and Feser One coolant (probably the best way to go is just distilled water and drain it every year or so, that way it's fresh).

Some mornings I would wake up to it working, others I get the 2 red CPU lights. One way to get it working is pressing the button right under the bottom slot of ram (and if the mac is on and you press that, the entire thing will power off), and usually it'll boot. Another thing I've had to do is take the LCS out and swap the top and bottom processors and run Apple Service Diagnostics 2.5.8 calibration for the fans, and that will help too. My other 2.7GHz G5 is just fine with the stock system, no issues. But this one that has issues, I'm going to find a set of air cooled heatsinks and see if that helps.

If you replace the coolant, be sure to have no air bubbles in there. Keep the system full and check on it every couple of days afterwards. When I did mine I had to pull it out a few hours later, drain the air, and force more coolant down the service hole. So the pump never runs dry!

Best of luck :)
 

Altemose

macrumors G3
Mar 26, 2013
9,173
480
Elkton, Maryland
I'll provide my feedback as I own a G5 with the crappy LCS. When I first got it, the thing would run but overheat. Took it apart, rebuilt it with new o-rings, 3/8 fuel line (a bit small on the inside, maybe cuts down on the pressure or something), and Feser One coolant (probably the best way to go is just distilled water and drain it every year or so, that way it's fresh).

Some mornings I would wake up to it working, others I get the 2 red CPU lights. One way to get it working is pressing the button right under the bottom slot of ram (and if the mac is on and you press that, the entire thing will power off), and usually it'll boot. Another thing I've had to do is take the LCS out and swap the top and bottom processors and run Apple Service Diagnostics 2.5.8 calibration for the fans, and that will help too. My other 2.7GHz G5 is just fine with the stock system, no issues. But this one that has issues, I'm going to find a set of air cooled heatsinks and see if that helps.

If you replace the coolant, be sure to have no air bubbles in there. Keep the system full and check on it every couple of days afterwards. When I did mine I had to pull it out a few hours later, drain the air, and force more coolant down the service hole. So the pump never runs dry!

Best of luck :)
Unfortunately, there are no bleeder valves on the LCS so you manually have to bleed the air out.
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
recharged the system pulled ram still no beeps

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pulled vid card again got the chime yay,thanks for all the help! One down one to go
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
chime on one G5, the other no go. pulled ram and vid card no boot chime. One with the chime got red light have to clean and repaste cpu's
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
ok one back up and running. The other no beeps no boot chime. Took out ram the vid card the added one stick of ram then all, then vid card still no boot chime. Disconnect hard drives and boot?

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still nothing
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
weii the one that is running will get hot and shut down, my guess is air in the LCS(already redid thermal grease-shin etsu). the second still no boot. Havent had much time for either out of town working
 

gavinstubbs09

macrumors 65816
Feb 17, 2013
1,386
249
NorCal boonies ~~~by Reno sorta
weii the one that is running will get hot and shut down, my guess is air in the LCS(already redid thermal grease-shin etsu). the second still no boot. Havent had much time for either out of town working
To really keep these machines running you gave two options. Rebuild the LCS (which is possible, but a lot of work and many curse words would be said), or get a set of dual 2.0/2.3 CPUs and their heatsinks then run Thermal Calibration. The LCS I guarantee you will have a bunch of crap in it just like the second one I ripped apart earlier this week.

This was everything (besides the little metal bit) that was living in the stock coolant, so flow was pretty bad causing the thing to overheat.
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
To really keep these machines running you gave two options. Rebuild the LCS (which is possible, but a lot of work and many curse words would be said), or get a set of dual 2.0/2.3 CPUs and their heatsinks then run Thermal Calibration. The LCS I guarantee you will have a bunch of crap in it just like the second one I ripped apart earlier this week.

This was everything (besides the little metal bit) that was living in the stock coolant, so flow was pretty bad causing the thing to overheat.
 

mark8

macrumors member
Original poster
Nov 29, 2010
77
1
WNY
Well back to the drawing board both G5's won't boot properly. Turn on with no boot and no white LED by power button took ram out and video card. Reset the pmu still no beeps or chimes.
 

JRDN

macrumors member
Oct 24, 2015
60
21
Well back to the drawing board both G5's won't boot properly. Turn on with no boot and no white LED by power button took ram out and video card. Reset the pmu still no beeps or chimes.

I picked up a cheap dual core G5 that wouldn't boot. It would start up. No chimes, then after 2-3 minutes the fans would go max rpm and still nothing.

Turns out the 6600 gpu was bad. swapped in a new one and it booted up just fine. Perhaps your vid card is bad?

I rebuilt my LCS from my Quad core a few months ago. The coolant inside is gross and smelled like fish. But I found that the small mesh filters that are in the cpu block were so clogged up that the coolant couldn't pass through it exacerbating the problem.

I took it apart. hooked up the radiator to a garden pond pump made a loop with a household water filter and ran distilled water and vinegar for a few hours.
Added clear watercooling fluid, killcoil, Tygon tubing, anti kink coils and put it all back together! One caveat, the pump is stuck on full RPM but it runs quite cool! ~40C on all cores idle

 
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